Age changes in lumbar vertebrae and intervertebral discs.

Reduction of stature in old age has been attributed to loss of disc height. A measurement study of 204 cadaveric lumbar spines from subjects ranging in age from one day to 97 years confirmed data on loss of "spinal stature" but could not confirm a loss of disc height. With aging, there is a progressive increase in vertebral end-plate concavity, associated with decreased bone density. These changes are more evident and take place earlier in females than in males. In the cancellous bone of vertebral bodies, a decrease in the number of horizontal trabecular "cross braces" leads to fracture of the vertical weight-bearing "beams" supporting the vertebral endplate. The intervertebral discs expand centrally and become increasingly convex. Measurements of average disc height demonstrate that loss of disc height is unusual in a normal, aging population. Only a minority of lower lumbar discs from elderly subjects show "thinning" and degeneration (beyond Rolander's Grade 2). Thus, loss of stature in the elderly is attributable to loss in vertebral height rather than loss in disc height. Dessication and thinning of discs, or discs that "bulge like underinflated automobile tires" are not typical of elderly spines.